Field of the Invention
The invention relates to an electromagnetic relay and, more particularly, to an electromagnetic relay including a magneto-electro converting device such as a Hall integrated circuit (Hall IC) or the like, and an energizing coil responsive to an electric signal for producing a magnetic field to drive the magneto-electro converting element.
Electromagnetic relays have been widely used in many applications which normally include one or more coils controlling one or more armatures each actuating electric contacts. However, such prior electromagnetic relays have had numerous disadvantages such as the use of contacts. First, bouncing and chattering occur in their switching operations. Second, there is a tendency of the contacts to be soiled with gas, dust, and soldering flux resulting in defective contact. Third, their service life is relatively limited due to the use of the contacts. In order to avoid or eliminate these disadvantages, contactless relays have been proposed, but they are incompetent in driving a large load.
Recently, input/output isolation has become an especially important factor in digital circuit designs. In view of this consideration, opto-couplers have been often used to couple digital circuits with superior electrical isolation which include a light source such as a light emission diode and a light detector such as a phototransistor housed in space relation in a single package. However, such opto-couplers have been found disadvantageous in that they are subjective to frequent failure or breakdown with an excessive voltage applied across the light emission diode or with an input signal reversely applied across the light emission diode and that they require such an adjustment that the phototransistor can receive a sufficient amount of light beam in order to maintain the S/N ratio.
In addition, for modern uses, size has become an increasingly important consideration. Small size units generally carry with them the additional advantages of lesser weight and smaller power consumption. The use of modern semiconductors can be a big advantage in reducing size, weight and power consumption. However, the advantages attendent upon the use of semiconductors are obtained only if they are operated within their electrical and thermal ratings.